The present invention relates to strapping machines for applying strap in a loop around an object, tensioning the strap, severing the supply portion and sealing together the ends of the tensioned loop.
More particularly, the present invention relates to a machine for applying plastic strap around an object, wherein the overlapping loop ends are secured together by heat sealing, the invention relating specifically to apparatus for guiding the strap to the sealing region from a strap supply and from the loop about the object.
A typical strapping machine of the type with which the present invention could be used is manufactured by Interlake, Inc., the assignee of the present invention, and is described in an Interlake instruction manual entitled "G18 Strapping Head" (Form 1256), copyright 1976. In that strapping machine, the guide members for guiding the plastic strap to the sealing region from the strap supply and from the loop around the object are typically formed of steel. Those guide members have exhibited an abrasive or cutting effect on the plastic strap being guided thereby. More particularly, it has been found that small pieces of the plastic strap have been abraded or chipped away by the guide members and have accumulated in the strap guide passage therethrough, thereby obstructing the path of the strap along the guide members and tending to jam the machine.
Some success has been experienced in overcoming this problem by chrome-plating the guide surfaces of the guide members, but this is a very expensive process and, therefore, has not proven to be economically feasible. A need has, therefore, arisen for a means to provide accurate guiding of the plastic strap through the strapping machine without adversely affecting the strap and at the same time providing essentially jam-free operation.